scholarly journals Design and Analysis of a Novel Microspeaker with Enhanced Low-Frequency SPL and Size Reduction

2020 ◽  
Vol 10 (24) ◽  
pp. 8902
Author(s):  
Ki-Hong Park ◽  
Zhi-Xiong Jiang ◽  
Sang-Moon Hwang
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Experimental Results ◽  
Multimedia Content ◽  
The Novel ◽  
Element Analysis ◽  
Low Frequencies ◽  
Acoustic Performance ◽  
Technological Developments ◽  
New Type

In the era of multimedia devices, smartphones have become the primary device for consuming multimedia content. As technological developments have facilitated a more immersive multimedia experience, enlarged displays and the use of several sensors have limited the allowable size of microspeakers. Although sound plays an important role when consuming multimedia content, the limited space for microspeakers in modern devices leads to poor acoustic performance, especially at low frequencies. To address this issue, this paper proposes a novel microspeaker structure that enhances the low-frequency sound pressure level (SPL), while also featuring reduced exterior dimensions. The structure was designed and analyzed using 3D finite element analysis. Through coupling analysis, the simulation results were verified on the basis of the experimental results. The novel microspeaker has one outer magnet surrounding the entire coil, unlike in prototype microspeakers, which have two outer magnets. The gap between the top plates and coil is reduced, and a new type of coil is introduced for the purpose of increasing electromagnetic force. The samples were manufactured, and their SPLs were tested in an anechoic chamber. The experimental results prove that the proposed microspeaker offers an improved SPL at low frequencies compared with prototype microspeakers.

A New Advanced Topology of Stacked Multicell Inverter

2014 ◽  
Vol 15 (4) ◽  
pp. 327-333 ◽  
Author(s):  
Mohamad R. Banaei ◽  
M. R. Jannati Oskuee ◽  
F. Mohajel Kazemi
Keyword(s):  
Frequency Spectrum ◽  
Output Voltage ◽  
Low Frequency ◽  
Experimental Results ◽  
The Novel ◽  
Stored Energy ◽  
Well Performance ◽  
Flying Capacitors ◽  
Voltage Frequency ◽  
Simulation Results

Abstract In this paper, a new advanced topology of stacked multicell inverter is proposed which is generally suitable for high number of steps associated with a low number of switches. Compared with traditional flying capacitor multicell and stacked multicell (SM) inverters, doubling the number of output voltage levels and the RMS value, ameliorating the output voltage frequency spectrum, decreasing the number and rating of components, stored energy and rating of flying capacitors are available with the proposed inverter. These improvements are achieved by adding only four low-frequency switches to the traditional SM inverter’s structure. The suggested topology is simulated using MATLAB/SIMULINK software, and simulation results are presented to indicate well-performance of the novel converter. In addition, the experimental results of proposed topology prototype have been presented to validate its practicability.

The Sound Environment of the Foetal Sheep

Behaviour ◽  
1982 ◽  
Vol 81 (2-4) ◽  
pp. 296-315 ◽  
Author(s):  
B.A. Baldwin ◽  
B.C.J. Moore ◽  
Sally E. Armitage ◽  
J. Toner ◽  
Margaret A. Vince
Keyword(s):  
Sound Pressure ◽  
Body Wall ◽  
Low Frequency ◽  
Sound Level ◽  
The Body ◽  
Human Foetus ◽  
Low Frequencies ◽  
Sound Environment ◽  
High Sound ◽  
Foetal Lamb

AbstractThe sound environment of the foetal lamb was recorded using a hydrophone implanted a few weeks before term in a small number of pregnant ewes. It was implanted inside the amniotic sac and sutured loosely to the foetal neck, to move with the foetus. Results differ from those reported earlier for the human foetus: sounds from the maternal cardiovascular system were picked up only rarely, at very low frequencies and at sound pressures around, or below, the human auditory threshold. Other sounds from within the mother occurred intermittently and rose to a high sound pressure only at frequencies above about 300 Hz. Sounds from outside the mother were picked up by the implanted hydrophone when the external sound level rose above 65-70 dB SPL, and the attenuation in sound pressure was rarely more than 30 dB and, especially at low frequencies, usually much less. However, attenuation due to the transmission of sound through the body wall and other tissues tended to change from time to time. It is concluded that the foetal lamb's sound environment consists of (1) intermittent low frequency sounds associated largely with the ewe's feeding and digestive processes and (2) sounds such as vocalisations from the flock, human voices and other sounds from outside the mother.

Innovative Design and Simulation for a Novel Vane Pump

2011 ◽  
Vol 328-330 ◽  
pp. 354-359
Author(s):  
Shi Biao Huang
Keyword(s):  
Finite Element Analysis ◽  
Optimized Design ◽  
The Novel ◽  
Analysis Software ◽  
Vane Pump ◽  
Element Analysis ◽  
Innovative Design ◽  
Novel Structure ◽  
Simulating Analysis ◽  
New Type

A novel structure of vane pump is brought forward, a new assembly relation among vane, sleeve, port plate and stator is created, mechanical bearing condition of new-type vane is preferable than traditional vane, vane is kept clearance with stator all the time as long as dimensions of those parts are reasonable. Modal analysis and optimized design for vane is made with finite element analysis software ANSYS. By simulating analysis for pump, simulation result shows that this novel vane pump is feasible. Compared with traditional pump, wear and vibration of novel vane pump can be reduced, volumetric efficiency of pump can be enhanced remarkably, the novel vane pump has certain application value.

Reduction of the Sound Pressure Radiated by a Submarine by Isolation of the End Caps

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Mauro Caresta ◽  
Nicole J. Kessissoglou
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Axial Direction ◽  
Radial Component ◽  
Axial Motion ◽  
Low Frequencies ◽  
End Caps ◽  
Passive Isolation ◽  
Radiated Sound ◽  
Finite Cylindrical Shell

A passive isolation approach to reduce the sound pressure radiated by a submarine is presented. The submerged vessel is modeled as a stiffened cylindrical hull partitioned by bulkheads and with two end caps of conical shape. Fluctuating forces from the propeller are transmitted to the hull through the shaft and a rigid foundation, resulting in axisymmetric excitation of the hull. The hull surface motion is mainly in the axial direction with a small radial component due to the coupling between the two orthogonal shell displacements. The sound pressure resulting from the axial motion is radiated from the end caps of the submarine. This work investigates reduction of the far field sound pressure by passive isolation of the end caps from the main hull. Isolation of the axial motion of the end caps from the cylindrical hull results in significant reduction of the radiated sound at low frequencies. The fluid loading approximation for a finite cylindrical shell in the low frequency range is also discussed.

scholarly journals Finite Element Analysis on Acoustic and Mechanical Performance of Flexible Perforated Honeycomb-Corrugation Hybrid Sandwich Panel

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jiaming Hu ◽  
Junyi Wang ◽  
Yu Xie ◽  
Chenzhi Shi ◽  
Yun Chen
Keyword(s):  
Finite Element ◽  
Sandwich Panel ◽  
Mechanical Performance ◽  
Mechanical Energy ◽  
Low Frequency ◽  
Rigid Wall ◽  
Acoustic Metamaterials ◽  
Mechanical Stiffness ◽  
Element Analysis ◽  
Low Frequencies

Since proposed, the perforated honeycomb-corrugation sandwich panel has attracted a lot of attention due to its superior broadband sound absorption at low frequencies and excellent mechanical stiffness/strength. However, most existing studies have assumed a structure made of high-strength materials and studied its performance based on the ideal rigid-wall model with little consideration for acoustic-structure interaction, thereby neglecting the structural vibrations caused by the material’s elasticity. In this paper, we developed a more realistic model considering the solid structural dynamics using the finite element method (FEM) and by applying aluminum and rubber as the structural material. The enhancement of the low-frequency performance and inhibition of broadband absorption coexisted in low-strength rubbers, implying a compromise in the selection of Young's modulus to balance these two influences. Further analysis on thermal-viscous dissipation, mechanical energy, and average structural stress indicated that the structure should work right below the resonant frequency for optimization. Based on these findings, we designed a novel aluminum-rubber composite structure possessing enhanced low-frequency absorption, high resistance to shear load, normal compression, and thermal expansion. Our research is expected to shed some light on noise control and the design of multifunctional acoustic metamaterials.

Low Frequency Calibration of Measurement Microphones

2009 ◽  
Vol 28 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Gunnar Rasmussen ◽  
Kim M. Nielson
Keyword(s):  
Frequency Response ◽  
Sound Pressure ◽  
Low Frequency ◽  
Constant Force ◽  
Low Frequencies ◽  
Proportional Relation ◽  
Frequency Calibration ◽  
Large Piston

The calibration of measurement microphones below 100 Hz is not very well covered by the present IEC standards. The uncertainty increases rapidly and for very low frequencies it goes toward infinity. This paper approaches this issue and presents a unique way to verifying and calibrating the low-frequency response of measurement microphones. Using a small isolated calibration volume and applying a constant force to a large piston inside this volume, you obtain a direct proportional relation between force and sound pressure, allowing calibration of measurement microphones down to 0.01 Hz.

Experiment Investigation of Magnetorheological Damper for High Impulsive Load

2010 ◽  
Author(s):  
Zhaochun Li ◽  
Jiong Wang
Keyword(s):  
Low Frequency ◽  
Mr Damper ◽  
Magnetorheological Damper ◽  
The Novel ◽  
Low Velocity ◽  
Impulsive Load ◽  
Signal Process ◽  
Impulsive Input ◽  
New Type ◽  
Long Stroke

In the past decade, magnetorheological (MR) damper, as a new type of smart damper, has gained significant findings which have led to good applications in the field of engineering. However, most of these work focused on low velocity and low frequency applications. This study provides an experimental investigation into a self-designed MR damper subject to high impulsive load. First of all, the active force of the recoil system in weapons is selected as an impulsive input of the MR damper. Then, a MR damper with long stroke of 440mm and single-ended construction especially for impact and high velocity is designed. The novel recoil apparatus is mainly composed of a MR damper and a series of springs. The measurement system includes transducers and the corresponding signal process equipments. Under the firing impulsive load, three currents including 1.0A, 1.5A and 2.0A are investigated. The results show that the peak force becomes larger when the current increases. On the other hand, the MR fluid is uncontrollable when velocity rises rapidly and it is not controllable until 0.026s.

A Design Method for Sound Absorbing Structure at Low Frequency

2020 ◽  
Vol 982 ◽  
pp. 39-50
Author(s):  
Ying Jie Fu ◽  
Xiao Ming Wang ◽  
Yu Lin Mei
Keyword(s):  
Design Method ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Channel Structure ◽  
Response Analysis ◽  
Acoustic Metamaterials ◽  
Element Analysis ◽  
Low Frequencies ◽  
Mass Unit ◽  
The Masses

Traditional acoustic absorbing materials are not effective for low-frequency engineering applications, but on the basis of the locally resonant principle, acoustic metamaterials can utilize the resonance of vibrators to dissipate acoustic energy and realize the subwavelength design of acoustic absorbers, therefore the acoustic metamaterials have great potential applications for noise reduction at low frequencies. This paper firstly employs the Bloch theory to investigate the effects of the parameters of the unit cell of the embedded membrane-and-mass metamaterials on the dispersion characteristics of the metamaterials, and the band gap is verified by the full wave finite element analysis. And then, a model of acoustic metamaterials is constructed by embeding an array of membrane-and-masses into a channel structure filled with acoustic materials. Next the transient frequency response analysis is performed to simulate the wave propagation in the model, the results show that the acoustic metamaterials can absorb the sound through the local resonance of the membrane-and-mass vibrators. Finally, an acoustic metamaterial maze structure is designed and analyzed, in the structure the membrane-and-mass array is embedded and the masses varies periodically. The research illustrates that the acoustic metamaterials with membrane-and-mass unit cells have excellent performances on the sound absorption at low frequency.

scholarly journals Muffler structure improvement based on acoustic finite element analysis

2019 ◽  
Vol 38 (2) ◽  
pp. 415-426 ◽  
Author(s):  
Jun Fu ◽  
Minghui Xu ◽  
Zengfeng Zhang ◽  
Wenjie Kang ◽  
Yong He
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Transmission Loss ◽  
Low Frequency ◽  
Analysis Method ◽  
Acoustic Attenuation ◽  
Element Analysis ◽  
Acoustic Performance ◽  
Finite Element Analysis Method ◽  
The Finite Element Analysis

Aiming to obtain the acoustic attenuation performance of exhaust muffler of diesel engine and the influence of main structural parameters on its acoustic attenuation characteristics, the finite element analysis method and acoustic theory were adopted to numerically investigate the acoustic attenuation performance under the boundary condition of acoustic adiabatic propagation and muffler wall. It suggested that the noise cancellation effect of muffler was poor at the middle and low frequency in range of 0–3000 Hz, and the transfer loss of muffler was basically 0 dB pass frequency at 1100 Hz. According to previous single-factor study experience, the structural factors, such as the expansion ratio, insertion length of outlet perforated pipe, the distance between the diaphragm and the front part of muffler, have influences on the acoustic performance of muffler at low frequency. Thus, they were taken as the starting point to study the influence of multiple interaction factors on the muffling performance by using orthogonal design method combined with the finite element analysis method. The influence degree of different structure parameters on the acoustic performance of muffler and the optimized structure parameters were obtained. Through the analysis on the acoustic characteristic of the optimized muffler, it indicated that the transmission loss of the improved muffler had significant increase in other frequency range except the range of 650–800 Hz and 2500–2700 Hz, especially at frequency of 1100 Hz compared with the original muffler. In the range of 0–3000 Hz, the mean of transmission loss of the improved muffler was about 9.8 dB larger than that of original muffler, which indicated that better noise cancellation effect was achieved. The improved muffler also provided a certain reference for the structural improvement of similar muffler.

Influence of Wall Surface and Air Modelling in Finite-Element Analysis of Sound Transmission Between Rooms in Lightweight Buildings

2012 ◽  
Author(s):  
Lars Vabbersgaard Andersen ◽  
Poul Henning Kirkegaard ◽  
Kristoffer Ahrens Dickow ◽  
Nikolaj Kiel ◽  
Kent Persson
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Acoustic Field ◽  
Degrees Of Freedom ◽  
Sound Pressure ◽  
Numerical Approach ◽  
Element Analysis ◽  
Low Frequencies ◽  
Infinite Elements ◽  
Rigorous Model

Noise is a nuisance in the built environment, and to avoid undesirable transmission of sound and vibration within a building, its vibro-acoustic performance must be addressed in the design phase. For heavy structures, a reliable assessment of the sound pressure levels can be made by statistical energy analysis—especially at high frequencies. However, for lightweight buildings a numerical approach, e.g. the finite-element method, must be applied. A problem in this regard is the computational complexity. Even at low frequencies, many degrees of freedom are required in a model accounting for all possible paths for transmission of sound in a building—in particular when finite elements are employed for the air. This paper examines whether a rigorous model of the acoustic field in each room is necessary in order to obtain accurate estimates of the sound pressure, or if a simpler approach may be adopted. Five different cases are compared: A model that only includes the structure, a model with semi-infinite elements to account for radiation from the structure into the air, a model introducing finite elements for the acoustic field, a model with dissipation of sound inside the room, and finally a model with sound absorption on the surfaces of walls, floors and ceilings.

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